16进制和字符串的相互转换

```c
char ptmp[128];
void strtohex(char *in, u8* out)
{
	int lengthp = 0;
	int lengthtmp = 0;
	int i = 0;
	memset(ptmp, 0, sizeof(ptmp));
	memset(out, 0, 57);
	lengthp = strlen(in);
	for (i = 0; i < lengthp; i++)
	{
		if (in[i] <= '9')	ptmp[i] = in[i] - '0';
		else if (in[i] > 'Z') ptmp[i] = in[i] - 'a' + 10;
		else ptmp[i] = in[i] - 'A' + 10;
	}
	for (i = 0; i < lengthp / 2; i++)
	{
		out[i] = (ptmp[i * 2] * 16) + ptmp[i * 2 + 1];		
	}
}
void hextostr(char*in, int len, u8* out) 
{
	char getdatatmp[3];
	int i = 0;
	memset(out, '\0', 57);
	for (i = 0; i < len; i++)
	{
		memset(getdatatmp, 0, sizeof(getdatatmp));
		sprintf(getdatatmp, "%02x", (unsigned char)in[i]);
		memcpy(&out[i * 2], getdatatmp, 2);
	}
}